1983 1.8 GTi DX Engine Running Issues

Rubjonny - I'm taking it to an MOT station later for an emissions test to find the real values.

However - interesting find is that the engine is in fact a Mk2 GTi PB engine (not DX) running k-jet. Does that affect anything I am doing? Quick search on the net doesnt suggest so…thanks as always.

makes no odds, the PB block is the same as a DX one, the head is similar you just have to swap the inserts for kjet ones so the injectors fit. the cam might not be quite as good as a proepr kjet one, but ive not seen any real evidence to support this

Thanks rubjonny - just as I thought - all seems to be in order.

So results from the emission check at the MOT station:

Adjusted to 1.8% CO content. Hydrocarbons at 2,000 ppm. Lambda at around 2.5. Corrected (?) CO was around 5.5%.

So it looks as though its over-fuelling - any suggestions of where to start?

Thanks for the continued help!

Does it run any better since the adjustments?

Hairyarse said

Does it run any better since the adjustments?

The short answer is no…when cold I cannot get the engine to idle high enough to continue running and so need to keep the idle up manually. When warm it appears to be OK at idle. Whilst driving it is spritely when accelerating but low-speed cruising around town is lumpy.

Sorry its not much to go on guys…I am now going round in circles!

Got new spark plugs to try as well as perhaps the injector delivery volumes - could the fuel pump be too powerful/delivering too much fuel? Thanks as always.

What type of unleaded fuel are you using?
Super or normal unleaded?

mark1gls said

What type of unleaded fuel are you using?
Super or normal unleaded?

Im running super unleaded based on reading some suggestions on the forum (always run it on super)…Tesco Ultimate 99 RON always.

Have you tried advancing the timing till it "pinks" under load (turn clockwise) then retard it a little so it stops "pinking" (turn anti clockwise)
You need to find a nice quite road to do this as you need to keep stopping and starting and listening with the window open, 20 mph in 3rd gear and slowly push the accelerator to the floor.
Make a mark where the dissy is set at the moment then you can always go back to how it is set up.
May not help with cold idle speed but may help with lumpy driving?
Did the garage set up the car for super unleaded?

Hi all - sorry for the long absence over winter. I have the car back on the road now, reset the mixture to around 1.8%, hydrocarbons down to around 200 PPM. It runs and sounds much better now but still unclear what the issue was.

One question - I have advanced the timing by 3 deg. Is this enough for super unleaded?

Thanks all for the help.

its a good place to start for sure, if the car drives well no pinking you can try a bit more then see, try a bit more etc till it pinks then back off. or if that seems like too much work just leave it as is